RAM 2500 Van V8-5.9L VIN Z (1997)
Spark Plug: Testing and Inspection
Broken, Cracked or Chipped Insulator
Chipped Electrode Insulator
A chipped electrode insulator usually results from bending the center electrode while adjusting the spark plug electrode gap. Under certain conditions,
severe detonation can also separate the insulator from the center electrode. Spark plugs with this condition must be replaced.
Brown to Gray/Tan Color - Normal Operating Condition
Normal Operation And Carbon Fouling
The few deposits present on the spark plug will probably be light tan or slightly gray in color. This is evident with most grades of commercial gasoline.
There will not be evidence of electrode burning. Gap growth will not average more than approximately 0.025 mm (.001 in) per 1600 km (1000 miles) of
operation. Spark plugs that have normal wear can usually be cleaned, have the electrodes filed, have the gap set and then be installed.
Some fuel refiners in several areas of the United States have introduced a manganese additive (MMT) for unleaded fuel. During combustion, fuel with
MMT causes the entire tip of the spark plug to be coated with a rust colored deposit. This rust color can be misdiagnosed as being caused by coolant in
the combustion chamber. Spark plug performance is not affected by MMT deposits.
Dry, Fluffy Black Deposits - Cold or Carbon Fouling
Normal Operation And Carbon Fouling
Cold fouling is sometimes referred to as carbon fouling. The deposits that cause cold fouling are basically carbon. A dry, black deposit on one or two
plugs in a set may be caused by sticking valves or defective spark plug cables. Cold (carbon) fouling of the entire set of spark plugs may be caused by a
clogged air filter or repeated short operating times (short trips).
